ETJPAGURUS. 543 



solid mass. It is impossible to unravel this tangle, and 

 the tube may or may not branch. 



It is from the epithelium lining this portion of the 

 testis that the gonadial elements arise. Some of the 

 germinal epithelium cells enlarge greatly and are budded 

 off into the lumen of the tube. These bodies have a large 

 quantity of densely staining nuclear matter and scanty 

 cytoplasm. They pass further down the tube, and each 

 divides into many smaller bodies with large deeply- 

 staining nuclei and again but little cytoplasm, and each 

 of these in turn gives rise to a single spermatozoon. The 

 former large bodies, which are more abundant in the 

 higher reaches of the tube, are known as the spermato- 

 cytes ; the smaller bodies formed by their division as the 

 spermatids. A typical section through a testis follicle 

 usually shows a large number of either spermatocytes or 

 spermatids with spermatozoa (fig. 46). It is not often 

 that both conditions are found in equal quantities in any 

 one portion of the tube. 



The spermatozoa continually pass down the 

 germinal portion of the tube into a smooth, thick- 

 walled area in which the chitinous cases for their 

 reception are secreted. The epithelial cells lining this 

 part are extremely long with oval nuclei situated at the 

 end of their outer third. The cavity has become 

 constricted and plum-stone shaped. The tube presently 

 emerges from the tangle and is seen to be a continuation 

 of the vas deferens. The portion in which the pre- 

 liminary process of forming the spermatophores is carried 

 on, lies in a very compact small coil on the surface of the 

 general mass of the testis at its posterior end (d. c, 

 fig. 40), and in this coil the sperms are surrounded by 

 a long smooth chitinous case, which is uninterruptedly 

 continued until the tube begins to leave the above- 



KK 



